Technical Field
The present invention relates to a writing instrument or an applicator including a plurality of resin molded parts formed by way of two-color molding.
Related Art
In the related art, a synthetic resin material is eagerly used for components constituting a writing instrument or an applicator. Most components of relatively low-price writing instruments or applicators such as body cylinders and caps are produced by injection molding using a resin material.
For example, a two-color molding method, in which a soft elastomer resin is secondarily formed around a body cylinder formed as a primary molding, has been widely used. In this manner, a grip part can be integrally formed with the body cylinder with ease to improve productivity.
Further, the two-color molding method can effectively be used for attaching, for example, a decorating part with a different color to a portion of the surface of a primarily formed member to differentiate the design of products.
The two-color molding method has been widely used for the writing instruments or applicators in the related art. However, all of those products have a relatively simple configuration in which a secondary molding is integrally formed on a surface of a primary molding (for example, see Japanese Patent Application Laid-Open Nos. 2004-291365 (Patent Literature 1) and 2005-193444 (Patent Literature 2)).
In recent years, writing instruments or applicators configured with many assembled resin parts have been provided. For example, the applicant provides a mechanical pencil in the market that can rotate a writing lead (refill lead) using writing pressure. This mechanical pencil includes a rotational drive mechanism for rotationally driving the writing lead.
The rotational drive mechanism included in the mechanical pencil includes a mechanism, for example, that mechanically allows parts each formed of a resin material to mutually slide in the axial direction every time writing pressure is applied to the writing lead. In this case, in order to form each part to have no play (looseness) in the sliding portion and to make relative movement smoothly, an extremely precise processing technique and strict control are required.